This invention relates generally to insecticides and more particularly to a topical insecticide, such as one suitable to use on house pets such as cats and dogs.
The infestation of animals with fleas, ticks, flies and the like is highly undesirable. Accordingly, it has become common to administer both topical and internal insecticides to livestock and pets. Topical applications can be desirable, in that many insecticides are acceptably safe when used topically, but not when used internally.
Various topical insecticides have drawbacks. Some require a large volume to be applied to the animal. This can cause considerable mess and can lead to an unpleasant smell. Also, when the animal is a house pet, there is a further complication in that the insecticide should be safe for human contact. It should also not lead to staining of furniture, carpeting and the like. Finally, even if safe, topical insecticides for house pets should not be irritating or lead to rashes, hair loss or exhibit other unpleasant side effects.
Natural and synthetic pyrethrins (pyrethroids) are known to provide strong insecticidal activity. They provide quick knock down and kill a variety of arthropod pests while remaining safe to humans and animals. However, many pyrethrins and pyrethroids are photo labile and are not stable in the presence of air and light (sunlight more so than indoor light) due to degradation; hence they quickly lose their knockdown and kill efficacy when exposed to light.
Various stabilizers have been proposed for formulating pyrethrins containing insecticides. However, there remains a need for an improved pyrethrin formulation for the treatment of topical ectoparasites on animals capable of withstanding photo-degradation (specifically light in the ultra-violet wavelength) for a sustained period of time. For example, U.S. Pat. No. 3,943,239 discloses a insecticidal formulation containing pyrethrins and a stabilizer. Although it confers thermal stability, it fails to protect the pyrethrin formulation after 2 days in sunlight.
Accordingly, it is desirable to provide an improved pyrethrins formulation, which overcomes drawbacks of the prior art.